dogs wont lock together

Question
i have 2 bichons, the male is 3 and the female is 5, they have preduced 2 litters in the past, and locked together fine, but the past 2 mateings, you can see that the male entered, but after 5 minutes has came out, they never locked, he did this twice in the same day, over 4 days, she never got pregnant in either times as they didnt lock. the male lives with my mum, and is NOT used to breed with other dogs.
why is he not swelling up?  

Answer
Hi Nicky

Have you checked him for Brucellois or STD's?  Has your female ever been bred with another male other than yours?

He could have a injury.  

It's best if you want to continue his lines as breeders, is to take him to the vet and have his semen checked.

Good luck